Test: Civil Engineering- 2

Fineness of cement is property of cement that indicate particle size of cement and specific surface area and indirectly effect heat of hydration. Fineness of cement affects hydration rate hence the rate of strength gain.

The smaller the particle size, the greater the surface area-to-volume ratio, and thus, the more area available for water-cement interaction per unit volume.

Therefore, finer cement reacts faster with water and the rate of development of strength and corresponding heat of hydration is high. Hence with increase in fineness of cement, rate of hydration increases but the total amount of heat generation will remain same.

Pigments are used to hide the surface imperfections and to impart the desired colour. They protect the paint film by reflecting the destructive ultraviolet light which acts as a catalytic agent for the destructive oxidation of the film.

Drier are used in paints for specific purpose e.g. as catalyst for the oxidation, polymerisation and condensation of the vehicle in paint. The quantity of drier is limited to 8%, excess of it affects the elasticity of paints leading to flaking failure.

Adulterants bring down the overall cost, reduce the weight and increase the durability. Adulterants also help to reduce cracking of dry paint and sometimes help to keep the pigment in suspension. Example Barium sulphate, calcium carbonate, magnesium carbonate etc.

Solvents are the oils used to thin the paints, increase the spread and are also known as thinners. Example-Spirit, naphtha and turpentine oil.

The fineness modulus is a numerical index of fineness which represents the mean size of the particles present in the aggregates.

As per IS 2386 (Part - I) - 1963, sieves used in calculating fineness modulus are:

80 mm, 40 mm, 20 mm, 10 mm, 4.75 mm, 2.36 mm, 1.18 mm, 600 μm, 300 μm and 150 μm.

Counting the sieve from finest one to identify the sieve corresponding to the fineness modulus of the sample.

For fineness modulus of 3.0, corresponding sieve is 600 μm.

Gauged mortar: It is a mixture of cement, lime, sand and water. The process of adding cement to lime mortar to improve its quality is termed as gauging and mortar thus prepared is known as gauged mortar.

Lightweight mortar: It is the type of mortar which is prepared by mixing saw dust, rice husk, jute fibers, coirs, asbestos fibers etc. along with sand and lime or cement.

Plastering thickness is marked by the Bull marks. For internal plastering 12 to 15 mm will be the average thickness. Plaster thickness, Plump, wall lines & right angles are considered while fixing Bull marks.

Bench mark is the point on the ground whose reduced level is known to us.

Kiln seasoning: Kiln is an airtight chamber, timber to be seasoned is placed inside it then fully saturated air with a temperature 35°C to 38°C is forced in the kiln. The heat gradually reaches inside timber. Then relative humidity is gradually reduced, and temperature is increased, and maintained till desired degree of moisture content is achieved. This method is used for seasoning on a larger scale for rapid seasoning.

Boiling: In this method timber is immersed in water and then water is boiled for 3 to 4 hours. Then it is dried slowly. Instead of boiling water hot steam may be circulated on timber. The process of seasoning is fast, but costly.

Air and water seasoning of timber are the natural process of seasoning.

Soundness of cement is affected by the presence of excess lime (CaO) in the cement. This excess lime hydrates very slowly and forms slaked lime that occupies a larger volume than the original free calcium oxide.

The slow hydration process, therefore, affects the properties of hardened concrete. The difference in the rate of hydration of free lime and slaked lime leads to change in volume of hardened concrete. The cement which exhibits this type of volume changes is described as unsound cement.

Shakes: Shakes are nothing but cracks which separates the wood fibres partly or completely. Depending upon the type of prevailing condition, different types of shakes are formed such as Cup shakes, Heart shakes, Ring shakes, Star shakes and Radial shakes.

Rind galls are curved swellings of trees which are formed at a point where a branch of the tress is improperly removed or fell down.

Knots: Knots are the most common defects caused due to natural forces. During the growth of a tree, branches close to the ground or lower branches die. Bases of those branches remain in the tree as the trees grow. These bases may create imperfection known as knots.

Twisted fibres: These are known as wandering hearts and caused by twisting of young trees by fast blowing wind. The timbers with twisted fibres are unsuitable for sawing.

Revised estimate is a detailed estimate and is required to be prepared under any one of the following circumstances:-

1) When the original sanctioned estimate is exceeded or likely to exceed by more than 5%.

2) When the expenditure on a work exceeds or likely to exceed the amount of administrative sanction by more than 10%.

3) When there are material deviation from the original proposal, even though the cost may be met from the sanctioned amount.

Rateable value: It is the net annual letting value of a property, which is obtained after deducting the amount of yearly repairs from the gross income.

Annuity: It is the annual periodic payments for repayments of the capital amount invested by a party.

Capitalised value: It is the amount of a money whose annual interest at the highest prevailing rate of interest will be equal to the net income from the property.

i) For fully glazed or gauged door, multiplying factor should be 0.80.

ii) For Flush door, multiplying factor should be 1.20.

iii) For Roof battens, multiplying factor should be 0.80.

iv) For steel rolling shutter’s, multiplying factor should be 1.10.

Sometimes a lump - sum rate is provided for certain small items for which detailed quantities cannot be taken out easily or it takes sufficient time to find the detail such as front architectural or decoration work of a building, fire place, site cleaning, dressing, Electrical installation and Contingencies etc.

Plastering of wall can be accurately measured that’s why it is not included in lump - sum items.

Work order: This is a contract and specifies the approximate quantities of different items of work, detailed specifications of each item of work, time for completion of the whole work, penalty etc. Small work up to Rs. 2,000 may be carried out by work order.

Cost plus percentage contract: In this type of contract, contractor is given certain percentage over the actual cost of the construction as his profit. Contractor arranges materials and labour at his cost and keeps proper account and he is paid by the department or owner the whole cost together with certain percentage, say 10% as his profit as agreed upon beforehand.

One m³ of mild steel weighs about 7850 kg

For 15 m³ of mild steel:

Weight = 15 × 7850 = 117750 kg

Outgoings are the expenses which are required to be incurred to maintain the revenue of the building. The various types of the outgoings are as follows:

i) Taxes: Municipal tax, Property tax, Wealth tax etc

ii) Repairs

iii) Management and collection charges

iv) Sinking fund

v) Loss of rent

vi) Miscellaneous: This includes electric charges for running lift, pump, for lightning common places etc

Note: Capital cost is the total cost of construction including land, or the original total amount required to possess a property. It is the original cost and does not change.

Capitalised value (V) of the property is given by:

V = Net income x Year purchase

Year purchase = 100/7.5 = 13.33

Net income = Rs. 1150

V = 1150 × 13.33 = Rs. 15333.33

i) Chief engineer has full power to technically sanction the work with no limits.

ii) Superintendent engineer has power to technically sanction the work up to rupees 1 crore.

iii) Executive Engineer has power to technically sanction the work up to rupees 40 lakhs.

iv) Junior Engineer has no power to technically sanction the work.

Remember the following test:

Spire test: It is a test carried out to remove Error due to non-perpendicularity of the horizontal axis and the vertical axis in surveying Instrument.

Crosshair ring Test: This test is done to make the vertical crosshair lie in a plane perpendicular to the horizontal axis.

Plate level Test: This test is done to make the plate bubbles central to their run when the vertical axis of the theodolite is truly vertical

Vertical arc Test: This test is done to make the vertical circle indicate zero when the line of sight is perpendicular to the vertical axis.

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight.

The temporary adjustments of a theodolite are:     

i) Setting over the station 

ii) Levelling up     

iii) Elimination of parallax

Elimination of parallax:

Focusing the eye-piece: To focus the eye-piece for distinct visions of the cross-hairs, hold a sheet of white paper in front of objective and move eyepiece in and out till the cross hairs are seen sharp and distinct.  

Focusing the objective: The Telescope is now directed towards the object to be sighted and the focusing screw is turned till the image appears clear and sharp.

Substance bar: A horizontal bar used in the subtense system of surveying by tacheometry. It is held at a distant point and its distance is calculated from its known length and the angle that it subtends at the observer's eye.

Tacheometry is one of the methods used in surveying to accurately measured the horizontal distance between two inaccessible points on the ground.

Horizontal distance from instrument station and ground point is given by:

D = ks + c

Where,

k = multiplying constant

i = stadia interval

f = focal length of the objective

k = f/i

c = additive constant

c = f + d

Number of links in 30 m chain is = 150

For 1 meter run,

Number of links per meter run = 150/30 = 5

Note: Number of links in 20 m, 10 m and 5 m chain is also 5.

Length in map = 0.12 m

Breadth in map = 0.07 m

Map area = 0.07 × 0.12 = 8.4 × 10^-3

Field area = 33600 m²

Representative scale = 

Porosity (η) is defined as the ratio of volume of voids to the total volume of the soil sample in a given soil mass.

The porosity of soils can vary widely.

The porosity of loose soils can be about η = 50 to 60%.

The porosity of compact soils is about η = 30 to 40%.

If the sand is in its densest state, then

e_o = e_min

Bulk density of partially saturated soil sample is given by:

Using the relation,

Se = wG

γ = 2.0 gm/cc

G = 2.65

The coefficient of Gradation is also known as the coefficient of curvature and It is given by

The slope of isochrones at any point at a given time indicates the rate of change of pore water pressure with depth. Within the consolidation process of a saturated clay a gradual decrease in neutral pressure and a gradual increase in effective pressure takes place and sum of the two is constant.

Hydraulic gradient (i) is defined as the head loss per unit length of the specimen.

h_f = 6 m

L = 50 m

Effective stress is equal to the total vertical reaction force transmitted at the points of contact of the soil grains divided by the total area, including that occupied by water. It is the pressure transmitted from particle to particle through their point of contact through the soil mass.

Silt is classified as C - ϕ soil. That’s why it has limited cohesive properties.

where,

C = Cohesion

ϕ = Angle of internal friction

For base failure depth factor, 

Where h height of the slope.

So for base failure 

For toe failure   

For face failure 

For same specific speed and working under the same head i.e. 

Hydraulic radius is given by = 

Area = 258 × 10³ cm²

Area = 25.8 m²

For steady, irrotational flow following two condition must be fulfilled:

i) flow possibility

ii) ω_z = 0 

  (flow is possible)
  (flow is irrotational)

For triangular weir or notch,

The percentage of CCA (culturable commanded area) proposed to be irrigated in a given season is called intensity of irrigation.

The annual irrigation intensity is usually found to be in the range of 40 to 60%. But needs to be raised in the range of 100 to 180% by cultivating larger parts of CCA with more than one crop in a year.

The first watering which is given to a crop, when the crop is a few centimetres high is called Kor watering.

The optimum depth of kor-watering for different crops are different.

For example:

i) The optimum depth of kor-watering for rice is 19 cm.

ii) The optimum depth of kor-watering for wheat is 13.5 cm.

iii) The optimum depth of kor-watering for sugarcane is 16.5 cm.

The duty of the water represents the relationship between the volume of water and the area of the crop it matures. It may be defined as the number of hectares of land irrigated for full growth of the crop by a supply of 1 m³/sec of water continuously during the entire base period of that crop.

Relation between Delta (∆) and Duty (D) is given by:

As the duty of canal is less, depth of water required (Known as delta ∆) will be more.

The limiting case of a unit hydrograph of zero duration is known as instantaneous unit hydrograph (IUH). The ordinate of one IUH at any time ‘t’ is the slope of S – curve of intensity 1 cm/hr.

Wooden, cast iron or R.C.C. members which are laid transverse to the track alignment to support the rails and to transfer the load from the rails to the underlying ballast are called sleepers.

Effective drainage to track is provided by ballast.

pH of the water can also be measured by certain indicators:

1.Phenolphthalein: Phenolphthalein indicator works in the pH range of 8.6-10.3. Phenolphthalein is often used as an indicator in acid-base titrations. For this application, it turns colourless in acidic solutions and pink in basic solutions, that's why if the pH of the water is more than 8.3 it turns the water into pink colour.

2.Methyl orange: Methyl orange indicator works in the pH range of 2.8-4.4. The original colour of this indicator is red and the final colour is yellow.

As per IS 1172:1993, water requirement for buildings other than residences are:

As per IS 10500:1991:

The desirable limit of total solid content in water for domestic purposes should not exceed 500 ppm.

In case of absence of alternate sources, the permissible limit specified is 2000 ppm.

Oxidation ponds are large, shallow typically 1-2 m deep, where raw or partially treated sewage is decomposed by microorganisms. The conditions are similar to those that prevail in a eutrophic lake.

This method would also have disadvantages that it requires extensive land area, potential odour problem, mosquito menace, little control over the effectiveness of the treatment process and the main disadvantage is seepage of effluents into soil which may also lead to ground water pollution.

Settling velocity, 

Where T = temperature in ^oC

From the equation V_s∝T

So as temperature increases the settling velocity also will increase.

Following are the disadvantages of traffic signals:

i) large stop time delay

ii) Complex signal design problems

The possible effect of poorly timed traffic signal is:

i) Increase in vehicle delay

ii) increases vehicle crashes particularly rear end crashes

iii) Disruption to traffic progression

Water bound macadam roads: 

The roads whose wearing course consist of clean crushed aggregates, mechanically interlocked by rolling and bound together with filler material and water and laid on a well-compacted base course, is called water bound macadam road.

Floating gradient:- The gradient on which a motor vehicle moving with a constant speed continues to descend with the same speed without any application of power brakes is called floating gradient i.e the vehicle does not require any tractive effort to maintain the specific speed.

Minimum gradient:- The minimum desirable slope essential for effective drainage of rainwater from the road surface is called minimum gradient

Exceptional gradient:- The gradient steeper than the limiting gradient which may be used in short length of road, only in an extraordinary situation is called exceptional gradient.

Ruling gradient:- The gradient usually adopted while making the road alignment is called the ruling gradient. It is the maximum gradient within which the designer attempts to design the vertical profile of a road. It is also known as design gradient.

Mechanical widening (W_m) on road is given by:

As width of pavement = 7.0 m, this implies number of lanes are 2.

So, n = 2

l = length of wheel base = 7.0 m (given)

R = radius of the curve = 490 m

Lacing system in a column is designed for transverse shear of 2.5 % of column load.

Design pressure is taken as:

C_pe = External pressure coefficients

C_pi = Internal pressure coefficients

For highly permeable buildings have more than 20 % openings,

C_pi = ±0.7

So,

P = ±0.7p

Coping: It is a course placed upon the exposed top of an external wall to prevent the seepage of water.

Cornice: It is a projecting ornamental course near the top of a building or at the junction of a wall and ceiling.

Lintel: It is a horizontal member of stone, brick, wood, iron or RCC used to support the masonry or load above an opening.

High early strength of cement is obtained as a result of:

1. Fine grinding

2. Increasing the lime content

3. Burning at higher temperatures

4. Decreasing the quantity of gypsum.

Basically, C₃S is responsilble for the early development of strength in the concrete.

Terrazzo flooring consists of:

i) Concrete bed

ii) Mortar bed, 1 cm of cement mortar (cement sand mixture 1 : 3)

iii) Metal strips

iv) marble chips 3 to 6 mm.

Mosaic flooring consists of Concrete layer, A layer of cementing material of about 3 mm thick (consisting 2 : 1 : 1 ratio of lime and marble and pozzolana material), marble pieces or tiles.

Marble flooring: Marble slabs are cut to get marble tiles of 20 to 25 mm thickness. They are laid on floors similar to other tiles. With power driven machine surface is polished to get even and shining surface. This type of flooring is widely used in hospitals and temples.

Bleeding is a form of segregation in which water present in the concrete mix is pushed upwards due to the settlement of cement and aggregate.

The specific gravity of water is low, due to this water tends to move upwards. Bleeding ordinarily occurs in the wet mix of concrete.

The Prime factor for bleeding in concrete is the high dosage of Water cement ratio. Higher water-cement ratio weakens concrete and leads to excessive bleeding.

Early bleeding when the concrete mass is fully plastic, may not cause much harm, because concrete being in a fully plastic condition, will get subsided and compacted. It is the delayed bleeding, when the concrete has lost its plasticity, which causes undue harm to the concrete. That’s why, Bleeding is good to an extent if it occurs when concrete is placed.

In bacterial concrete when cracks appear in a concrete structure and water starts to seep in through, the spores of the bacteria start microbial activities on contact with the water and oxygen. In the process of precipitating calcite crystals through the nitrogen cycle, the soluble nutrients are is converted to insoluble CaCO₃ and remediate the cracks.

Compaction significantly increases the ultimate strength of concrete and enhances the bond with reinforcement. It also increases the abrasion resistance and general durability of the concrete, decreases the permeability and helps to minimise its shrinkage and creep characteristics.

Proper compaction also ensures that the reinforcement, tendons and fixings are completely surrounded by dense concrete, the formwork is completely filled i.e. there are no pockets of honey-combed material and that the required surface finish is obtained on vertical surfaces.

For most of concrete mixes, over-vibration creates the problem of segregation in which the denser aggregates settle to the bottom while the lighter cement paste tends to move upwards.

Curing of cement concrete is defined as the process of maintaining the moisture and temperature conditions of concrete for hydration reaction to normal so that concrete develops hardened properties over time.

The time to start curing of concrete depends on the evaporation rate of moisture from the concrete. The evaporation rate is influenced by wind, radiant energy from sunshine, concrete temperature, climatic conditions, relative humidity.

According to Indian standard specification,

Concrete should be cured under a humidity of 90%.

Impact strength of concrete is assessed usually by the ability of a concrete specimen to withstand repeated blows and to absorb energy.

The impact strength of water stored concrete is found to be lower than when the concrete is dry.

For the same compressive strength, impact strength is greater for concrete made with coarse aggregate of greater angularity and surface roughness. Angularity number for angular crushed aggregate is more than that of rounded aggregate, therefore impact strength of angular crushed aggregate is more than that of rounded aggregates.

Bulking Of Sand: The volume of dry sand increases due to absorption of moisture. 

The concrete mix proportion is 1:3:6,

Let volume of cement to be 1 m³

Then,

Volume of sand = 3 x 1 m³ = 3 m³

The volume of coarse aggregate = 6 m³

Incorporating 15 % bulking of sand,

Volume of sand required per unit volume of cement is = 1.15 x 3 = 3.45 m³

Required sand is greater in case of bulking than in case of normal condition.

The static modulus of elasticity does not truly represent the elastic behaviour of concrete due to the phenomenon of creep. Ultrasonic pulse velocity measures the dynamic modulus of elasticity which is higher than those determined by static method because the dynamic method is unaffected by creep.

The degree of hydration is synonymous with the age of concrete provided the concrete has not been allowed to dry out or the temperature is too low. It is seen that majority of strength gain by concrete is achieved in 28 days and the rest is continuous throughout the life of concrete. Concrete mainly gains strength by hydration of water present in it, this will lead to decrease in water cement ratio and increase in strength of concrete.

Therefore, Strength of concrete increases with age.

As per IS 456: 2000 clause 10.2.2,

The accuracy of the measuring equipment shall be within ±2% of the quantity of cement being measured.

The accuracy of the measuring equipment shall be within ±3 % of the quantity of aggregate, admixtures and water being measured.

For cantilever and continuous beam the ratio of span to depth to satisfy stiffness criterion shall not exceed 7 and 26 respectively.

(clause 23.2.1 of IS: 456-2000)

In case of eccentrically loaded struts, there is bending stress along with direct axial stress and the twisting moment is also acting on the structure. The hollow section has more moment of inertia, so hollow section is preferred in case of an eccentrically loaded strut.

As per clause 26.2.2.1, the anchorage value of standard U type hook shall be equal to 16 times the diameter of the bar.

So anchorage value is 256 mm.

Flat slab is supported on columns monolithically built with slab. Flat slab is provided when there is a restriction to provide beams due to space constraint and when large openings are desirable for better natural lighting. 

As per IS 456:2000:

The bond strength of HYSD bars is 60% more than the bond strength of mild steel bars for the same grade of concrete used.

So, if mild steel bars are used in place of HYSD steel bars, the bond strength of concrete decreases but development length required will be more.

The slenderness ratio of the wall is lesser of 

So, slenderness ratio of the wall is 19.

The thermal expansion coefficient of steel (α_steel) is equal to thermal expansion coefficient of concrete α_concrete.

α_steel = α_concrete = 12 × 10^-6/^oC

That’s why RCC is widely used in civil engineering practise.

Compared to plain bars, the deformed bars will have a better bond due to corrugation. The ultimate and yield strength of deformed bars are higher than that of plain bars (mild steel bars), so the design with deformed bar is also economical. 

The short column will fail by crushing or yielding of material.

The load carrying capacity of short column is = Stress in concrete x area of concrete + stress in steel x area of steel 

Side face reinforcement in the web of the beam is provided when the depth of the web in a beam exceeds 750 mm. (0.1% of the web area and shall be distributed equally on two faces at a spacing not exceeding 300 mm or web thickness whichever is less).

The elastic strain energy stored in a member of length s (it may be curved or straight) due to axial force, bending moment, shear force and torsion is summarized below:

Strain energy due to combined effect of load P and torque T:

Torsion Formula:

Thus the maximum twisting moment a shaft is the product of the permissible shear stress and polar modulus (ratio of the polar moment of inertia to the radius of the shaft).

Elongation of rod is given by:

P = 3000 kg

E = 2.1 × 10⁶ kg/cm²

D = diameter = 2 cm

L = length = 5 m

The following assumptions are made in the Euler’s column theory about long column:

• The column is initially perfectly straight, and the load is applied axially
• The cross-section of the column is uniform throughout its length
• The column material is perfectly elastic, homogeneous and isotropic and obeys Hooke’s law
• The length of the column is very large as compared to its lateral dimensions
• The direct stress is very small as compared to the bending stress.
• The column will fail by buckling alone
• The self-weight of the column is negligible

From the simple bending theory equation:

If σ_b is the maximum bending stresses due to bending moment M on shaft:

For same bending moment:

So σ_A = 2 σ_B

In the case of bi-axial state of normal stresses:

Normal stress on an inclined plane:

Shear Stress on an inclined plane:

Normal stress on 45° plane:

Proof resilience is defined as the maximum energy that can be absorbed within the elastic limit, without creating a permanent distortion.

The modulus of resilience is defined as the maximum energy that can be absorbed per unit volume without creating a permanent distortion (i.e. The proof resilience per unit volume of a body is called modulus of resilience).

In some applications the shaft are simultaneously subjected to bending moment M and Torque T.

From the simple bending theory equation:

If σ_b is the maximum bending stresses due to bending moment M on shaft:

Torsion equation:

The maximum shear stress developed on the surface of the shaft due to twisting moment T:

Equivalent Bending Moment:

Equivalent Torque:

D_s = D_se + D_si – R

Where D_se = External indeterminacy = r – 3

D_si = Internal indeterminacy = m – (2j – 3)

R = Release = 0

∴ D_se = 3– 3 = 0

D_si = 11 – (2 × 6 – 3) = 11 – 9 = 2

∴ D_s = D_se + D_si – R

= 2

D_c = m – 2j + 3

= 9 – 12 + 3 = 0; i.e. the frame is statically determinate.

D_k = 2j – 3 – m

= 12 – 3 – 9 = 0; i.e. the frame is kinematically determinate.